Superclusters as Nondissipative Pancakes

Abstract

The formation of aspherical superclusters (SC’s) is studied by 3-D N-body simulations that are confronted with the Local SC (LSC), and a simple model is developed. A nondissipative scenario, in which galaxies are formed from perturbations on smaller scales prior to the collapse of SC’s, is found to be successful. It explains the disk-halo structure of SC’s, their flattening and their low dispersions, which are nontransient because of the expansion along the long axes. The LSC has collapsed at z≤0.5. The large-scale velocity isotropy and the local 1-D infall indicate Ω<1. The correlation of galaxies on a few Mpc scales grows nonselfsimilarly due to recent pancaking rather than gradual clustering. This may be tested by the lack of clustering among objects at z>1.